The present invention relates to a method of detection of DNA and protein and of DNA base sequencing determination and to an apparatus therefor.
It relates more particularly to the fluorescence detection type gel electrophoresis apparatus.
For DNA base sequencing determination by electrophoresis gel separation, a radioisotope label has been used as a label for a DNA fragment. Due to the inconvenience of this method, however, a method of using a fluorescence label has come to be increasingly employed. (Refer to U.S. patent application Ser. No. 07/506,986 (U.S. Pat. No. 5,062,942) and Bio/Technology Vol 6, July 1988, pp816-821, for example.) As an excitation light source this method uses an argon laser with an output of 20 to 50 mw and a wavelength of 488 nm or 515 nm to detect the DNA fragment of 10.sup.-16 mole/band to 2.times.10.sup.-18 mole/band. As fluorophores, the method has used FITC (fluorescein isothiocyanate with a maximum emission wavelength of 515 nm), SF (succinyl fluorescein with a maximum emission wavelength of 510 nm to 540 nm), TRITC (tetrarhodamine isothiocyanate with a maximum emission wavelength of 580 nm) and Texas Red (sulforhodamine 101: a maximum emission wavelength of 615 nm).
Normally, electrophoresis is performed with polyacrylamide gel placed on the plate which is provided between two glass plates. In recent years the capillary gel electrophoresis method has been developed, where gel is formed in the capillary. Use of a capillary having a smaller diameter increases the surface area per volume of gel; this feature facilities the dissipation of Joule heat, permitting application of high voltage. A high-speed electrophoresis separation is provided by the capillary gel electrophoresis method.
The first example of the capillary gel electrophoresis method as a prior art is described in Nucleic Acid Research, Vol. 18. pp. 1415 to 1419 (1990), Journal of Chromatography, Vol. 516, pp. 61-67 (1990), and Science, Vol. 242, pp. 562-564 (1988). Another method of using one migration lane for base sequence determination is disclosed in Nature Vol. 321, pp. 674-679 (1986) and others.
The above-mentioned conventional technique, however, has disadvantages in that the sensitivity is insufficient, and the entire equipment must be made greater in size because the Ar laser is greater in size than a He--Ne laser.